Flexible manufacturing systems (FMS) such as large industrial printers can be modeled as re-entrant flow-shops with a set of constraints of processing times, setup times and relative due dates. This is a non-deterministic system in which the actual values for these constraints can be different from the ones originally estimated. Therefore, a way to quickly determine the ranges of constraint values for which a given schedule becomes feasible or infeasible can become highly useful. In this paper, a heuristic algorithm is proposed that can efficiently split the zones of feasibility for a given schedule. With the right settings, an accuracy of 99.9% can be achieved with relatively few queries on 2-dimensional examples.